Rietveld refinement of Ba(5)(AsO(4))(3)Cl from high-resolution synchrotron data

The apatite-type compound Ba(5)(AsO(4))(3)Cl, penta­barium tris­[arsenate(V)] chloride, has been synthesized by ion exchange at high temperature from a synthetic sample of mimetite (Pb(5)(AsO(4))(3)Cl) with BaCO(3) as a by-product. The results of the Rietveld refinement, based on high resolution synchrotron X-ray powder diffraction data, show that the title compound crystallizes in the same structure as other halogenoapatites with general formula A (5)(YO(4))(3) X (A = divalent cation, Y = penta­valent cation, X = Cl, Br) in space group P6(3)/m. The structure consists of isolated tetra­hedral AsO(4) (3−) anions (m symmetry), separated by two crystallographically independent Ba(2+) cations that are located on mirror planes and threefold rotation axes, respectively. The Cl(−) anions are at the 2b sites ([Image: see text] symmetry) and are located in the channels of the structure.